1. Field of the Invention
The present invention relates to a structure for cooling a power drive unit for controlling the operation of a motor-generator connected to an engine and functioning as either a motor or a generator.
2. Description of the Related Art
There is a system, as disclosed in Japanese Patent Application Laid-open No. 11-257115, in which a motor-generator functioning as either a motor or a generator is connected to an engine, in which it functions as a motor to assist in the starting of the engine or in a driving force from the engine, and it functions as a generator to generate power by the driving force from the engine or to generate a power by regenerative braking.
Such a power drive unit for the motor-generator controls a large amount of current, using a large-sized switching element and hence, in order to prevent a reduction in durability of the power drive unit due to the heating of the power drive unit, it is necessary to sufficiently cool the power drive unit. In the conventionally known system, the power drive unit is accommodated in an engine room and, for this reason, there is a possibility that the power drive unit receives heat generated by the engine in addition to heat generated by itself, resulting in a rise in temperature thereof, and the cooling of the power drive unit is insufficient.
The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to enhance the effect of cooling the power drive unit for controlling the operation of the motor-generator connected to the engine.
To achieve the above object, in the present invention there is provided a structure for cooling a power drive unit for an automobile for controlling the operation of a motor-generator connected to an engine and functioning as either a motor or a generator. The structure includes a power drive unit-accommodating chamber, which is defined outside a side frame disposed on a side of an engine room with the engine accommodated therein in a widthwise direction of a vehicle, so that it is separated from the engine room, and the power drive unit is accommodated in the power drive unit-accommodating chamber, so that it is cooled by travel wind.
With the above arrangement, the power drive unit-accommodating chamber is defined outside the side frame disposed on the side of the engine room in the widthwise direction of the vehicle, and the power drive unit accommodated in the power drive unit-accommodating chamber is cooled by the travel wind. Therefore, the power drive unit in the power drive unit-accommodating chamber separated from the engine room receives only a small amount of the heat generated by the engine and, moreover, is cooled effectively by the travel wind, leading to an enhanced cooling effect. In addition, the power drive unit is disposed outside the engine room and, hence, the layout of other auxiliary parts within the engine room is easily achieved.
A heat shield plate is preferably disposed between the engine room and the power drive unit-accommodating chamber.
With the above arrangement, heat generated by the engine can be shielded by an effect of the heat shield plate disposed between the engine room and the power drive unit-accommodating chamber, thereby further effectively preventing a rise in temperature of the power drive unit.
The power drive unit preferably includes a cooling device adapted to perform the heat exchange with the travel wind through cooling water.
With the above arrangement, the cooling device adapted to perform the heat exchange with the travel wind through cooling water is provided on the power drive unit and hence, the effect of cooling the power drive unit can be further enhanced.
The power drive unit and the cooling device are preferably formed integrally with each other and mounted to a vehicle body.
With the above arrangement, the power drive unit and the cooling device are formed integrally with each other and mounted to the vehicle body and hence, as compared with a case where they are separately attached to the vehicle body, the number of mounting steps and the number of mounted parts can be reduced.